The present invention relates to an assumption torque setting device for setting, in an internal combustion engine that executes a torque reduction process during a gear shifting period, a torque assumed to be output by the internal combustion engine that is based on a target torque from which an amount corresponding to the torque reduction process is excluded as an assumption torque during the gear shifting period. The present invention also relates to an automatic transmission controller using the assumption torque setting device. Further, the present invention relates to a method for learning or determination of an internal combustion engine delay model that can be applied to the assumption torque setting device and the automatic transmission controller.
Japanese Laid-Open Patent Publication No. 5-280625 (pp. 4-5, FIG. 7) proposes a technique for holding a line pressure in an automatic transmission calculated from an input torque when a gear shifting period starts (e.g., gear shifting period after inertia phase) and controlling the automatic transmission with the held line pressure during the subsequent gear shifting period to stabilize gearshift control.
The engine load may greatly change due to a change in throttle opening during the gear shifting period in which the line pressure is held for stable control of the automatic transmission. In such a case, this would increase the difference between the line pressure actually required when completing the gear shifting period and the held line pressure and thereby produce a gear shifting shock. To prevent such a shock, Japanese Laid-Open Patent Publication No. 2006-329217 (pp. 11-16, FIGS. 6 to 17) proposes a technique for setting a hypothetical engine torque based on the acceleration pedal during the gear shifting period.
However, in the technique of Japanese Laid-Open Patent Publication No. 2006-329217, during a gear shifting period, the hypothetical engine torque is set to be close to the target torque, which is obtained from the operation state of the internal combustion engine, particularly, the depression amount of the acceleration pedal. Thus, the response state of the actual output torque relative to the target torque in the internal combustion engine is not taken into consideration, and the hypothetical engine torque is not accurate. Accordingly, the automatic transmission control based on such hypothetical engine torque is not accurate, and therefore a step is formed between the hypothetical engine torque and the actual torque when gear shifting is completed. This may produce gear shifting shock.